i opted for a insulin drip during labour which my diabetes consultant figured out a sliding scale for the midwives and that worked perfectly. otherwise with a pump your partner has to be sure they are confident to do blood tests and be able to change pump if needed which wasnt too sure if i wanted to deal with....
As soon as you have your baby you go back to your pump settings pre-pregnancy, i didnt have any hypos post birth. only pre birth was having a struggle
im surprised you're able to have a water birth...in the hospital that i was in was a absolute no no with being classed as high risk
all the very best for you and your little one